1. Field of the Invention
The present invention relates to a reproduction of a multimedia transport stream for broadcasting and, more particularly, to a method and an apparatus of adjusting the output and output priority time of caption information included in a received multimedia transport stream for broadcasting.
2. Description of the Related Art
A broadcasting reception apparatus, such as a set-top box (STB) and a digital TV, receives a digital broadcasting signal through a sky wave or a satellite. The digital broadcasting signal is a transport stream obtained by multiplexing video, audio, and data information complying with the moving picture experts group (MPEG) standard, and is received in units of packets by the broadcasting reception apparatus. In particular, the data information includes caption information for additional functions, such as a caption, teletext, and advertisement, which are output together with video and/or audio information. When digital broadcasting is watched, the caption information can provide a variety of additional functions. For example, in case of foreign language broadcasting, the contents of a voice currently being output can be displayed in a foreign language caption. This is very convenient for users who want to study the foreign language. Also, though sometimes the sign language is shown on a part of the screen for deaf or hard of hearing people, the caption information can be used to display a caption for these people.
The video and audio signals decoded in the broadcasting reception apparatus are output, by synchronizing the video and audio output time points by using presentation timestamps (hereinafter referred to as PTS) included in video and audio packets, respectively. However, in case of the data packet for the caption information, the data packet is received and begins to be decoded later than the video packet or the audio packet. Accordingly, since the presentation time is late, the data packet may not correspond with the video screen.
Therefore, it is needed that a data signal including caption information is output after being accurately synchronized with the video and audio signals. Meanwhile, for the purpose of the foreign language study, in order to display a caption after audio information is output, or in order to output audio information after a caption is first displayed, it may be necessary for a user to arbitrarily adjust the output time of the caption information.
Meanwhile, with the development of digital broadcasting technologies, caption information can be output together with audio, such as subtitle, teletext, and advertisement. When a plurality of caption information items are provided at the same time to users, those items are overlapped according to provided broadcasting programs, such that the caption information cannot be smoothly used.